Means for preventing fretting erosion



Allg- 4 1964 E. N. BAMBERGER ETAL. 3,143,383

MEANS FOR PREVENTING FRETTING EROSION Filed July 21. 1961 azi/AZ 41656 MAI/,wu 10i,

United States Patent O 3,143,383 MEANS FOR PREVENTING FRETTING ERGSN Eric .N. Bambergen Cincinnati, Ghia, and Filhert E. Spinelli, Scotia, N.Y., assignors to General Electric Company, a corporation of New York Filed Juiy 21, 1961, Ser. No. 125,667 S Claims. (Cl. 308-241) The present invention relates to means for preventing fretting erosion, and more particularly is concerned with a new and improved combination comprising two abutting members, one of which has its contacting surface provided with a new and improved anti-fret coating material. In addition, the present invention pertains to a new and irnproved method for preventing fretting erosion at the contacting surfaces of two abutting members.

Fretting may be dened as the erosion occurring at the contacting surface portions of two abutting members which are subjected to vibratory, oscillating or other types of sliding motion. The contact surface portions of a member which has experienced fretting will generally be characterized by severe pitting and oxidation at the area of contact. The pits and cracks formed as a consequence of fretting are believed to be stress concentration points which eventually may lead to fatigue failure. Additionally, fretting will result in a loss of dimensional tolerance in many of the closely tted members, as well as a loosening of parts which should remain secured for the successful operation thereof.

Concern over the effects of fretting, and particularly the fretting encountered at the high temperatures attained in a host of technological endeavors has become quite acute in recent years. For example, the phenomenon of fretting has been a constant problem relative to the successful operation of the high mach aircraft gas turbine where many carefully dimensioned parts function in intimate contact at elevated temperatures and at high frequency vibratory conditions. In such applications, the parts subjected to fretting erosion are generally constructed of high tempera- 4ture resistant alloys which may include, among others, one or more of the metals iron, nickel and cobalt. The fretting occurring at the contacting surface portions of members which are subjected to the elevated temperatures attained during engine operation may often necessitate a repeated examination and replacement of costly parts, and further may in certain instances require a literal overhaul of the engine itself.

Although the enigmatic problem of fretting has long been recognized, and a variety of expositions concerning its causes have been rendered, a solution to the problem satisfactory from both the standpoint of simplicity as well as economy heretofore has been unavailable in the prior art. A variety of schemes, of course, have been proposed for alleviating or reducing the effects of fretting. One such method, disclosed in U.S. Patent 2,787,503, issued to Palsulich et al., suggests the coating of the surface of one of two abutting members with molybdenum, and coating the contact surface of the other member with a layer of pure copper or a copper alloy containing in addition, the metals lead and zinc. However, the requirement of coating both contacting surfaces may in certain instances be prohibitive from the standpoint of economy. The high cost of molybdenum further detracts from the practicability of such a scheme. Additionally, pure copper7 or a high copper containing alloy including lead and zinc may not, from a practical standpoint be sufficiently adherent to some of the high temperature alloys employed, such as those, for example, used in the high mach turbojet engines.

Accordingly, it is the primary object of the present invention to provide new and improved means for preventing fretting erosion.

Another object of the present invention is to provide a new and improved combination comprising two abutting members, one of which has its contacting surface provided with a new and improved anti-fret material.

A further object of the present invention is to provide a new and improved combination comprising two abutting members at least the contacting surface of the first of which is constructed of an alloy including a metal selected from the group consisting of iron, nickel and cobalt, the other member having its contacting surface coated with a new and improved anti-fret material.

Still another object of the present invention is to provide a new and improved method for preventing fretting erosion.

Another object of the present invention is to provide a new and improved method for preventing fretting erosion at the contacting surface of a member at least the contacting surface of which is constructed of an alloy including at least one of the metals iron, nickel and cobalt.

The drawing is a fragmentary, partially sectional view of a combination of a rotating gas turbine blading member and a rotating wheel member with an anti-fret coating between the members at critical surfaces of contact.

Briefly stated, these and other objects which will appear hereinafter are attained in accordance with the present invention by providing a new and improved combination comprising two members having opposed contacting surfaces, at least the contacting surface of the first of said members comprising an alloy including at least one metal selected from the group consisting of iron, nickel and cobalt, and an anti-fret coating comprising, in percent by weight, 20-40 percent nickel, 2-10 percent indium, with the balance essentially copper bonded to the contacting surface of the second member.

The new and improved method of the present invention for preventing fretting at the contacting surfaces of two abutting members wherein at least the contacting surface of the first member is constructed of an alloy of at least one metal selected from the group consisting of iron, nickel and cobalt, comprises coating the surface p0rtion of the second member with an alloy comprising, in percent by weight, 20-40 percent nickel, 2-10 percent indium, with the balance essentially copper to provide a tenaciously bonded anti-fret coating thereon.

As stated above, the need for a practical solution to the problem of fretting encountered with high temperature resistant alloys of the type including iron, nickel and cobalt has become especially acute within recent years. A variety of coating materials such as, for example, rhenium, pure copper or copper-lead-tin alloys have been tested in conjunction with such high temperature alloy materials with little or no success. It was discovered that the use of the new and improved brazing alloy material disclosed in U.S. Patent 2,988,447-Hoppin, assigned to the same assignee as is the present invention, aorded a remarkable improvement over the use of any of the anti-fret materials heretofore employed in the prior art, and further was particularly eiicacious in the prevention of fretting erosion when used to coat a contact surface which, in operation, was mated with an opposing surface comprising an alloy of at least one metal selected from the group consisting of iron, nickel, and cobalt. As will be appreciated by those skilled in the art, the abutting member which is to mate with a surface provided with the new and improved anti-fret coating in accordance with the present invention may be constructed entirely of an alloy including at least one metal selected from the group consisting of iron, nickel, and cobalt, or alternatively may have only its contact surface portion provided with such an alloy. From the standpoint of economy, however, the invention is particularly benelicial where the entire member is constructed of such an alloy since, of course, the coating of the contacting surface portion is obviated in such a case.

A variety of materials may be used to provide the substrate, or base member which is to be coated with the anti-fret alloy in accordance with the present invention. In general, the only requirement that need be met is that the anti-fret alloy coating form a tenacious bond with the substrate, so that the coating will be relatively unaffected at the oscillating and possibly high temperature conditions of a particular installation. However, it has been found highly advantageous to employ in certain instances hard facing alloys including the high temperature resistant alloys of any one of the refractory metals. Alloys such as, for example, those including one of the metals iron, nickel, cobalt chromium, tungsten, tantalum, columbium and molybdenum have been found to be particularly receptive to the anti-fret alloy as used in accordance with the present invention inasmuch as they form a fine metallurgical bond therewith and are therefore preferred materials from which the coated member of the new and improved combination of the present invention may be selected.

As stated above, the new and improved method of the present invention for preventing fretting erosion comprises coating the contact surface of one of two abutting members with an alloy comprising, in percent by weight, 20-40 percent nickel, 2-10 percent indium, with the balance essentially copper to provide a tenaciously bonded anti-fret coating thereon. The surface thus provided, when mated with an opposing contacting surface comprising an alloy of at least one of the metals iron, nickel, and cobalt provides complete protection against the fretting erosion, which would otherwise be experienced. In this regard, it should be noted that a variety of coating techniques may be employed to provide the new and improved antifret coating in accordance with the present invention. A preferred method of coating, however, and one which provides a extremely fine bond between the coating and the underlying substrate comprises tiame spraying, and preferably of the plasma arc type, the anti-fret alloy material directly onto the substrate which forms the opposing or mating surface with an alloy of one of the metals iron, 'nickel yor cobalt. Additionally, it may be preferable in certain instances to grit-blast the surface to be coated prior to ame spraying, so as to roughen that surface and thus enhance the bonding of the coating to the substrate. It should be understood, however, that other coating methods such as, for example, vapor deposition, and dip coating from a molten bath may also be employed, and are considered to lie within the spirit of the invention and the scope of the appended claims.

It should also be noted that the thickness of the applied anti-fret coating may vary within a wide range. Generally, however, thicknesses ranging from 0.001 inch to 0.003 inch have been found to be satisfactory although, of course, thicker coatings may be applied depending upon the requirements of a particular installation.

As mentioned above, the new and improved anti-fret alloy comprises, in percent by weight, 20-40 percent nick- TABLE I [Nominal composition in percent by weight] Cu Ni In Balance 37 10 Do. 39 5 Do. 40 3 Do. 39 5 Do. 40 5 D0. 35 5 Do. 35 5 Do. 30 5 Do. 30 2 Do. 30 3 D0. 30 4 In order that those skilled in the art may better understand how the present invention may be practiced, the following examples are given by way of illustration and not by way of limitation. All parts and percentages are by weight unless otherwise noted. Fretting tests were con ducted by providing an oscillating motion between two members, a stationary shoe member and a reciprocating sliden The amplitude of the motion ranged up to 0.100 inch, and frequencies from about 10 cycles per minute up to about 30,000 cycles per minute were employed. Pressures of up to about 25,000 p.s.i. were applied to the test specimens and were maintained throughout the entire test period, which in each case lasted about one hour. Test temperature ranged from room temperature up to about 1200 F.

Example 1 A surface of a high temperature resistant iron alloy member having a composition, by weight, of C-0.08% max., Mn-1-2%, Si-0.41%, Cr-13.5-16%, Ni-24- 27%, Mo-l-1.5%, Ti-1.9-2.3%, B-0.0030.01%, with the balance essentially Fe, waws prepared for coating by grit-blasting the surface with a #25 mesh sharp angular steel grit at an air pressure of about 65 p.s.i. so as to roughen that surface and enhance the bonding of the subsequently sprayed alloy to the substrate. A plasma flame unit was then utilized to spray the anti-fret alloy comprising 60 percent copper, 35 percent nickel and 5 percent indium onto the roughened surface. The alloy was sprayed in powder form of a particle size ranging from -200 to +300 mesh. A percent nitrogen-10 percent hydrogen gas mixture was used to produce the plasma flame. Power input to the gun was 28 kilowatts which produced plasma temperatures at the nozzle orifice of the order of 9500 F. The applied alloy layer was approximately 0.002 inches thick (-1- or 0.0005 inch).

In the present example, the copper-nickel-indium a1- loy coated component comprised the slider member which was rubbed against a stationary shoe member consisting essentially of the same iron alloy. The contact surface portion of the shoe was not coated, however. A fretting test was then .conducted in which an amplitude of 0.02 inch and a frequency of 1200 c.p.m. were used. 1200 p.s.i. of pressure were applied to the test specimens and maintained throughout the duration of the test, which lasted about one hour. The test temperature was ap- Example 2 The contacting surface portion of a slider member constructed of an alloy of the composition, by weight, of C-0.04%, Cr-%, 'Ti-2.4%, A1-0.6%, 13e-7%, with the balance essentially Ni was coated with an alloy consisting, by weight, essentially of 35 percent nickel, 5 percent indium, with the remainder copper. The mating shoe member was constructed of a nickel base alloy of the composition, by weight, of C-0.08%, Cr-15.5%, rl`i-2.5%, Al-0.7%, Fe 7%, Cb and Ta 0.95% with the balance essentially Ni and Co. A etting test was conducted in the same manner as in Example 1, and the contacting surface portions of the test specimens were thereafter carefully examined. As in Example 1, the anti-fret alloy coating appeared slightly polished but was absolutely free of any evidence of fretting erosion. The contacting surface of the mating shoe member was also unaffected and was entirely devoid of any pitting whatsoever. The results of the test were excellent.

Example 3 The contacting surface portion of a slider constructed of an alloy consisting, by weight, essentially of C-0.04%, Cr-l5%, 'Ti-2.4%, tl-0.6%, lle-7%, with the balance Ni, was llame sprayed with a 0.002 inch thick layer of an alloy consisting, by Weight, essentially of 39 percent nickel, 5 percent indium with the balance essentially copper. A fretting test of the type outlined in Example l was thereafter conducted. In the present case, the stationary shoe member was constructed of a cobalt base alloy consisting, by weight, essentially of C-0.15% max., Cr-%, lli-10%, Mn-l.5%, W-15%, Feb- 3% max., with the balance Co. Results of the test were excellent. No evidence of any fretting in the form of pitting or galling was observed at the contacting surface of either the shoe or the coated slider specimens.

Example 4 In this case, the contacting surface portion of a shoe member constructed of an alloy consisting, by weight, essentially of C-0.08% max., Mn-l-2%, Si-0.4-1%, Cr-13.516%, Ni-24-27%, Mo-1-1.5%, 'Ti-1.9- 23%, V-t).1-5%, B-0.0030.01%, with the balance Fe was coated with an anti-fret alloy of the composition, by weight, of 30 percent nickel, 2 percent indium, with the balance essentially copper. The mating slider specimen that was used in the fretting test was constructed of a nickel base alloy consisting, by weight, essentially of C0.08%, Cr-15.5%, Ti-2.5%, rtl-0.7%, Fe- 7%, Cb and Ta-0.95%, with the balance Ni and Co. An examination of the contacting surfaces after completion of the test revealed no signs of any type of erosion Whatever at those surfaces. Accordingly, the results were excellent.

Example 5 The contacting surface of a shoe member of the type used in Example 4 was coated with an alloy consisting, by Weight, essentially of 35 percent nickel, 5 percent indium and the balance copper. The mating slider specimen used in this case was a cobalt base alloy consisting, by weight, essentially of C-0.l5% max., Cr-20%, Ni-l0%, Mn-l 5%, W-l5%, Fe-3% max., with the balance Co. As in Example 1, the coated shoe contact surface was slight polished and no evidence of fretting on either surface was discernable.

The results of the tests as reported in Examples 1-5 are summarized in the following Table l1:

TABLE II Compositions Example Results Slider Shoe Coating 1.-- Iron al1oy* Iron alloy 351%Nb5% ln, Excellent a u. 2 Nickel all0y* Nickel alloy do Do. 3 d0 Cobalt alloy-. 39% Ni, 5% In, Do.

bal. Cu. 4 do Iron alloy* 30% Ni, 2% In, Do.

bal. Cu. 5 Cobalt alloy-; do* 35% Ni, 5% In, D0.

bal. Cu.

Designates specimen which was provided with the antifret coating.

It should be noted that in each of the foregoing examples, excellent results were obtained by providing a copper-nickel-indium alloy coating on the contacting surface which mated with a surface comprising an alloy of one of the metals, iron, nickel, and cobalt. On the other hand, tests conducted with specimens neither one of which was provided with the new and improved anti-fret coating in accordance with the present invention revealed serious pitting and galling to have taken place on the contacting surfaces tested. Additionally, a 65 weight percent copper-35 weight percent nickel powdered mixture flame sprayed onto the contacting surface of a slider member of the type described in Example 1 afforded no protection against fretting, inasmuch as severe pitting and galling were observed at the contacting surface of the coated specimen as well as the iron alloy shoe member which was mated therewith for the purposes of the tests.

As will be appreciated by those skilled in the art, the new and improved combination of the present invention may comprise any two abutting members, at least the surface portion of one of which comprises an alloy including at least one metal selected from the group consisting of iron, nickel and cobalt, and the other of which has its contacting surface coated with the anti-fret alloy described above. lt should be understood, therefore, that although the new and improved combination of the present invention has particular utility in the prevention of fretting in parts such as those, for example, used in high mach turbo jet engines, it may also be employed in a variety of technological installations and, in fact, wherever fretting of a surface constructed of an alloy including at least one of the metals iron, nickel and cobalt is a problem. Further, it is emphasized that the present invention is not to be considered limited to any of the specic embodiments herein described, but may be used in other ways without departure from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. The combination which comprises: two substantially stationary members having opposed contacting surfaces; the contacting surface of the first of said members comprising a metal selected from the group consisting of iron, nickel, cobalt, iron base alloys, nickel base alloys and cobalt base alloys; and the contacting surface of the second of said members comprising an anti-fret coating comprising, by weight, 20-40 percent nickel, 2-10 percent indium, with the balance essentially copper bonded to the second of said members.

2. The combination which comprises: two substantially stationary members having opposed contacting surfaces; the contacting surface of the first of said members comprising a metal selected from the group consisting of iron, nickel, cobalt, iron base alloys, nickel base alloys and cobalt base alloys; the second of said members comprising as its principal element a metal selected from the group consisting of iron, nickel, cobalt, chromium, tungsten, tantalum, columbium, molybdenum, and having an anti-fret coating comprising, by Weight, 20-40 percent nickel, 2-10 percent indium, with the balance essentially copper, metallurgically bonded to its contacting surface.

3. The combination which comprises: two substantially stationary members having opposed contacting surfaces; the contacting surface of the rst of said members consisting essentially of a metal selected from the group consisting ofv iron, nickel, cobalt, iron base alloys, nickel base alloys and cobalt base alloys; md the contacting .surface of the second of'said members consisting essentially of an anti-fret coating consisting, by weight,

essentially of 30-35 percent nickel, 2-5 percent indium, with the balance copper bonded to the contacting surface of the second of said members.

5. The combination which comprises: two substantially stationary members having opposed contacting surfaces; the contacting surface of the first of said members consisting essentially of a metal selected from the group consisting of iron, nickel, cobalt, iron base alloys, nickel base alloys and cobalt base alloys; and the contacting surface of the second of said members consisting essentially of an anti-fret coating consisting, by Weight, essentially of 35 percent nickel, 5 percent indium, with the balance copper bonded to the contacting surface of the second ofsaid members.

6. The combination which comprises: two substantially stationary members having opposed contacting surfaces; the contacting surface of the rst of said members consisting essentially of a metal selected from the group consisting of iron, nickel, cobalt, iron base alloys, nickel base alloys and cobalt base alloys; the second of said members consisting essentially of as its principal element a metal selected from the group consisting of iron, nickel, cobalt, chromium, tungsten, tantalum, columbium, molybdenum, and having an anti-fret coating consisting by weight, essentially of 35-40 percent nickel, 3-5 percent indium, with the balance copper metallurgically bonded to its contacting surface.

7. The combination which comprises: two substantially stationary members having opposed contacting surfaces; the contacting surface of the rst of said members consisting essentially of a metal selected from the group consisting of iron, nickel, cobalt,y iron base alloys, nickel base alloys and cobalt base alloys; the second of said members consisting essentially of as its principal element a metal selected from the group consisting of iron, nickel, cobalt, chromium, tungsten, tantalum, columbium, molybdenum and having an anti-fret coating consisting, by weight essentially of .3G-35 percent nickel, 2-5 percent indium, with the balance copper metallurgically bonded to its contacting surface.

8. The combination which comprises two substantially stationary members having opposed contacting surfaces; the contacting surface of the first of said members consisting essentially of a metal selected from the group consisting of iron, nickel, cobalt, iron base alloys, nickel base alloys and cobalt base alloys; the second of said members consisting essentially of as its principal element a metal selected from the group consisting of iron, nickel, cobalt, chromium tungsten, tantalum, columbium, molybdenum alloys and having an anti-fret coating consisting by weight, essentially of 35 percent nickel, 5 percent indium, with the balance copper metallurgically bonded to its contacting surface.Y

Queneau et al May 13, 1941 Palsulich et al. Apr. 2, 1957 

1. THE COMBINATION WHICH COMPRISES: TWO SUBSTANTIALLY STATIONARY MEMBERS HAVING OPPOSED CONTACTING SURFACES; THE CONTACTING SURFACE OF THE FIRST OF SAID MEMBERS COMPRISING A METAL SELECTED FROM THE GROUP CONSISTING OF IRON, NICKEL, COBALT, IRON BASE ALLOYS, NICKEL BASE ALLOYS AND COBALT BASE ALLOYS; AND THE CONTACTING SURFACE OF THE SECOND OF SAID MEMBERS COMPRISING AN ANTI-FRET COATING COMPRISING, BY WEIGHT, 20-40 PERCENT NICKEL, 2-10 PERCENT 